As to a PC (Personal Computer), a retrieval function is a general technique widely used in daily business. For example, Web retrieval to retrieve information related with a specified keyword from a Web site on Internet is used by many persons. In the retrieval function with the PC, by inputting a keyword related with things (retrieval objects) from a user, a retrieval result is acquired. Briefly, a retrieval method which the user need actively input the keyword is ordinary. Hereinafter, this retrieval method is called “active retrieval method”. Furthermore, IT (Information Technology) of an AV equipment (such as a TV, a DVD recorder, a HDD recorder) is progressing, and the AV equipment is connectable with an Internet. Accompanying with this, the AV equipment prepares the active retrieval function same as the PC.
However, an ability to store a content in the AV equipment, a service of Video-On-Demand (VOD), and a seamlessness of the content between equipments (outside of the AV equipment) or the Internet, are enlarged, and the number of contents accessible by the user increases quickly. Furthermore, the user's style to acquire and view the content by spread of the HDD recorder is changing. Briefly, a style to record the user's desired content is changing as a style to previously record the user's interest contents and select the user's favorite one from the contents, or a passive style (a recommendation service, an automatic recording service). Accordingly, the contents accessible by the user often include one which the user cannot understand.
On the other hand, it is an important problem to effectively select the user's desired content from a group of contents accessible by the AV equipment. As mentioned-above, the user does not always understand all contents because the style to acquire and view the content is changing. Accordingly, when the user retrieves the content using the active retrieval function, the user suitably select a retrieval keyword, and it is difficult for the user to effectively retrieve the user's desired content.
Furthermore, as to the AV equipment, a user is not always strong in the PC. In other words, the user is not always familiar with the active retrieval of keyword input type, which is a general function in the PC. As a result, the active retrieval method in the AV equipment is a function only used by a partial active user. Briefly, this method is not convenient for many users.
In order to solve above-mentioned problem, instead of the active retrieval method, a passive retrieval method is used. As to the passive retrieval method, for example, contents related with some content are presented, and the user selects his/her favorite one from the presented contents (called “relational contents”). In this method, the user's desired content is not actively (positively) searched using the keyword. By setting some content as a retrieval source, relevancy between this content and other contents is presented to the user, and the user implicitly retrieves his/her desired content from the other contents.
Briefly, the user retrieves his/her favorite content without an explicit keyword. As a result, as to a plurality of contents accessible by the AV equipment, while watching a visualized result of relevance among the plurality of contents, the user can passively select the desired one. In this way, in the passive retrieval method, it is very important for the user to visualize the relevancy between contents.
On the other hand, in a field of photograph, various techniques to visualize relationship among a large number of images (taken by a digital camera) are proposed. For example, in WO 00/33572 (Kokai) ( . . . Patent Reference 1), in order to represent a relationship among a plurality of images in time series, the plurality of images is enlarged in order of time series, and spirally displayed from an inner circle to an outer circle in order of time series.
However, as to a dynamic image such as the TV or the video, which is an object of the AV equipment, the image of each frame is changing in order while playing, and the relevancy between images is also changing dynamically. In the technique disclosed in the Patent Reference 1, the dynamic image cannot be processed because a static image is a processing object. Accordingly, as to the content (the dynamic image) changeable with passage of time, it is desired that the relevancy among contents is visualized with the change.